1. Field of the Invention
The present invention relates to heat transporting apparatus, more particularly to a pump-free water-cooling system that requires no external power supply such as a mechanical pump.
2. Description of the Related Art
In recent years, the calorific values of electronic apparatuses have rapidly been increasing; therefore, higher-efficiency heat radiating means have been required. In addition, the life times of the electronic apparatuses have been prolonged; therefore, higher-reliability heat radiating means have been required. Under this background, heat pipes without moving parts (e.g., refer to Patent Reference 1) have been drawing attention again. Heat pipes are roughly divided into two types, i.e., gravity-type heat pipes (thermosiphon) and capillary-type heat pipes. In a gravity-type heat pipe, an appropriate amount of working fluid is enclosed in an airtight container; and the lower portion of the gravity-type heat pipe joins with a heating element while its upper portion joins with a heat radiating portion, or is directly disposed in cooling fluid. In contrast, in a capillary-type heat pipe, an appropriate amount of working fluid is enclosed in an airtight container with grooves on its inner wall, or in an airtight container with porous substance covering its inner wall; and one end of the capillary-type heat pipe joins with a heating element while the other end joins with a heat radiating portion, or is directly disposed in cooling fluid.
Because the capillary-type heat pipe that has the structure described above refluxes working fluid to a heating portion (a portion in which a heating element is disposed) by means of capillary force, i.e., extremely small driving force, its maximal heat transportation capacity is small, and it is difficult to reflux the working fluid in the direction reverse to gravity direction; therefore, the problem of difficulty in transporting heat has been posed. In contrast, because a gravity-type heat pipe refluxes working fluid to a heating portion by utilizing gravity, there was limitation of posture, i.e., that the heat radiating portion must definitely be situated higher than the heating element; therefore, a problem has been posed wherein there was no degree of freedom in terms of installation posture.